A general mixing-precipitation model describing interactions between mixing of various scales (macro-, meso- and micromixing) coupled with the population balance for crystallization is presented. Macro-, meso- and micromixing were interpreted as a circulation through the zones of different rate of energy dissipation, inertial-convective disintegration of large eddies and an engulfment of fluid from the environment, respectively. The model was verified experimentally for double feed semibatch BaSO4 precipitation. Experiments were carried out in a Rushton type stirred rank reactor. The effects of feed tube positions, addition feed rate, intensity of mixing, initial reagent concentration and volume ratio on particle size distribution and particle morphology were investigated. The model enables prediction of supersaturation profiles in the system and resulting CSD; the predicted history of supersaturation structure explains the influence of operating conditions on crystal morphology.